They like to rest on the leaves of their plants. Nothing to worry about.

My bettas are forever climbing onto the floating indian almond leaves in their bowls to go to sleep, amazing to see, I have tried several times to take photos, but soon as I get near enough to take a decent snap, they swim off, soon as I capture a decent picture I will post it.

I have one pland suction cupped to the side of my aquarium so that it dangles from out of the water down into it. My betta loves to climb up on the edge of it at night, just below the water surface. I guess that makes for easy breathing breaks while he tries to sleep at night. Instead of swimming to the surface he just has to arch his back a bit to get a breath.